Thesis Details

Thesis Title:

A comparison of the performance of cryogenically-treated and untreated knitting elements

Thesis Author:

Norman M. Parker, IV

Abstract:

Open-end rotor spun yarn is widely used in the knitting
industry. These yarns, however, have been shown to
accelerate knitting element wear. Service life of needles
and sinkers, when processing open-end yarn, has been
reduced to as little as four weeks, compared to at least
six months when processing ring-spun yarn.
The purpose of this thesis was to compare the
performance of cryogenically-treated and untreated knitting
elements and to explain the effect of treatment on
high-carbon steel parts. The work included a plant trial,
wear simulation tests, and metallurgical tests. Samples of
the plant trial knitting elements were measured for wear,
analyzed microscopically, and photographed. Wear
simulation testing was used to confirm the results of the
plant trial. Metallurgical tests (microhardness and x-ray
diffraction) were used to explain the effect of the
treatment on the knitting elements.
All results confirmed that the cryogenic treatment does
impart enhanced wear characteristics to the knitting
elements. The treated needles were less worn and more
uniform compared to untreated needles in both the plant
trial and in wear simulation. Treated sinkers were also
less worn than untreated sinkers. But the sinker cams, at the end of the plant trial, did not show any differences in
wear as a result of the treatment.
The plant trial also revealed that mixing treated and
untreated needles and sinkers deteriorated the wear
performance. Best results were obtained when both the
needles and sinkers were treated.
Fabric samples taken from the plant trial revealed that
treated needles produced a more attractive fabric with
increased cover compared to fabric produced from untreated
needles. This is attributed to an increasing greige wale
count with treated needles and a decreasing greige wale
count with untreated needles as a result of the wear
characteristics of the needles. The course count for both
fabrics remained constant.
Metallurgical testing revealed that cryogenic treatment
is most effective when treating parts with substantial
levels of retained austenite. If a needle, sinker, or
sinker cam has little or no retained austenite in the
untreated state, very little improvement can be expected.
This thesis proved that 9ryogenic treatment of certain
knitting elements can be used to combat the accelerated
wear caused by open-end rotor yarn.